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Peak expiratory flow

Breathing tests · PEFR · also printed as PEF, Peak flow, Peak expiratory flow rate, PEFR (L/min), Peak flow rate

Typical UK adult rangeNo single typical range

No fixed range; compare with the printed predicted value or personal best.

What this test measures

Peak flow is the fastest speed of air blown out in a single hard breath. It is a simple measure of how open the large airways are, and people with asthma often track it at home.

Why doctors request it

Used in asthma to follow control and to compare with a personal best.

What commonly pushes it up

There is no problem with a high value

What commonly pushes it down

Asthma, especially when poorly controlled
COPD
Poor technique

Everyday reasons for a value outside the range

The predicted value depends on age, sex and height
Morning values are naturally lower than evening ones
The personal best matters more than the predicted value

About the sample

Best of three blows, standing. Read against the personal best.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.

Got a report with Peak expiratory flow on it?

Upload a photo or PDF and see every line against the range your lab printed, explained in plain English. First report free.

Read my report free

This is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.